A neck portion of a rotating tool (a portion between a holder end and a cutting tooth in a case where the rotating tool is mounted to a machine tool) comprises a shank, and a small diameter section formed smaller in diameter than a shank diameter. The small diameter section is provided in order to avoid interference with a workpiece as described in Japanese Patent Application Laid-open No. 2002-283120.
The rotating tool provided with the small diameter section in this way is increased in an amount of protruding from a processing machine, accordingly, runout of the rotating tool is therefore easy to occur at the time of processing, thus, as long as the interference with the workpiece can be avoided, it is desired that the length of the small diameter section is minimized.
However, a commercially available rotating tool has a small diameter section whose length is set to only predetermined intervals (for example, intervals of 5 mm), so that even if the length of the small diameter section is selected in order to avoid the interference with the workpiece, in some cases, an unnecessary allowance is added to a distance which can avoid the interference between the shank and the workpiece.
Moreover, as compared with a standard product, in which a length of the small diameter section is set to a standard length, there is a slight demand for a special product, in which a length of the small diameter section is set to be longer or shorter than that of the standard product, and the number of stocks thereof is also small, so that the cost thereof is high and it is hard to obtain it.
For this reason, a user of a rotating tool adjusts the length of the small diameter section by grinding the inexpensive standard product or the special product, the length of the small diameter section is short.